Scala Boolean to String conversions
This is because Boolean
isn't a subtype of String
or type compatible with String
scala> val a: Any = "Hello"
a: Any = Hello
scala> val b = a.asInstanceOf[String]
b: String = Hello
scala> val c: Char = 123
c: Char = {
scala> val d = c.asInstanceOf[Int]
d: Int = 123
scala> (123).asInstanceOf[Double]
res0: Double = 123.0
scala> (1.3).asInstanceOf[Int]
res1: Int = 1
As you can see, I can easily cast any type compatible types back and forth, in this case numbers (including chars) are cross compatible. All types are compatible with Any
, because Any
just holds any arbitrary object reference, so as long as you "unbox" using the right types, you're golden.
scala> val arr = Array("Hello", 245, true)
arr: Array[Any] = Array(Hello, 245, true)
scala> val first = arr(0).asInstanceOf[String]
first: String = Hello
scala> val second = arr(1).asInstanceOf[Int]
second: Int = 245
scala> val third = arr(2).asInstanceOf[Boolean]
third: Boolean = true
This works fine, and as long as you're careful with how you unbox, you won't get any errors. This is how you'd do it in Java before generics were introduced to the language. That said, if you cast any one of the array elements to the wrong type, you'll get the cast exception.
The .toString
method is different from a type cast, in that it's not a cast at all, it exists to serve as a concise way of converting any object, to a string representation of itself.
scala> val a = List(1,2,3,4)
a: List[Int] = List(1, 2, 3, 4)
scala> a.toString
res0: String = List(1, 2, 3, 4)
This is done so that any type can be printed if necessary, and has nothing to do with casting.
elm
Updated on June 07, 2022Comments
-
elm almost 2 years
One way to convert
true: Boolean
onto a String isscala> true.toString res: String = true
However,
scala> true.asInstanceOf[String] java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String
Why the latter attempt fails ?
Many Thanks